How much does a dormer loft conversion cost? (2026 guide)
A loft conversion is one of the best ways to add a bedroom without losing any garden, and the dormer is the type most homeowners end up choosing. If you are considering one, this guide explains what a dormer conversion costs and what you get for the money. As FMB-registered builders with over 20 years of experience in Solihull and the West Midlands, we design and build dormer conversions from structural work through to the finished room.
What is a dormer loft conversion?
A dormer conversion extends outward from the existing roof slope to form a box shaped addition, usually at the rear of the house. That box creates vertical walls and a flat or shallow roof, which adds valuable head height and floor area compared with simply putting windows into the existing slope. It is the type that most reliably turns an awkward loft into a proper, comfortable room.
How much does a dormer loft conversion cost?
The ranges below are a realistic guide for Solihull and the wider West Midlands, covering the conversion to a good standard.
| Project | Indicative cost |
|---|---|
| Dormer loft conversion | £40,000 to £65,000 |
| Roof light conversion | £28,000 to £45,000 |
| Hip to gable conversion | £45,000 to £70,000 |
Figures are indicative UK ranges to help you budget and are not a quote. Actual costs depend on size, specification and site conditions.
For a full comparison of every type, see our guide to loft conversion types.
What affects the cost of a dormer conversion?
The biggest factor is the size and style of the dormer. A single, modest rear dormer sits towards the lower end of the range, while a large, full width dormer that spans the back of the house costs more because it involves more structure, roofing and glazing. Other factors include the finish of the new room, whether you add an en-suite, the position and number of windows, and how the new staircase is arranged to reach the loft. Ground and roof structure can also affect the amount of strengthening work needed.
What does a dormer loft conversion give you?
The most common result is a double bedroom with an en-suite, which is one of the highest return improvements you can make to a home. The extra head height a dormer provides is what makes this possible, giving you a room you can stand up and move around in comfortably rather than a cramped space under the slope. Some homeowners use the space as a large home office or a quiet living room instead.
Does a dormer loft conversion need planning permission?
Many rear dormer conversions fall under permitted development and do not need a full planning application, provided they stay within the size and height limits. Dormers on the front of a property, or homes in conservation areas, are more likely to need planning permission. We confirm which applies to your home before starting. Our planning permission guide covers this in detail.
What building regulations apply to a dormer conversion?
Every loft conversion needs building regulations approval, regardless of whether it needs planning permission. This covers the structural work, the new staircase, fire safety, insulation and ventilation. It is what makes the new room safe, legal and straightforward to sell in the future, and we manage the building control process from start to finish.
Does a dormer loft conversion add value?
Yes. A loft conversion that adds a proper double bedroom and en-suite is consistently one of the highest return home improvements, often returning more than it costs when done well. A dormer is particularly good for value because it creates a genuinely usable room rather than a cramped space, and usable space is what adds to a property price. The quality of the finish and how neatly the dormer sits on the roof both matter, so a careful design and a tidy build are worth paying for.
Is a dormer the right choice for your home?
A dormer suits most houses with a reasonable roof, and it is often the best balance of cost, space and simplicity. If your loft already has excellent head height, a simpler roof light conversion might be enough. If your roof slopes on the side, a hip to gable conversion, sometimes combined with a dormer, may give you more room. We help you weigh these up honestly during a free site visit.
How long does a dormer conversion take?
Most dormer conversions take around six to eight weeks on site depending on size and specification. We give you a clear programme before we begin. You can explore our full conversions service or read our advice on planning permission first.
Get a free quote
Every project is different, so the most reliable way to get an accurate price is a free, no obligation site visit. As FMB-registered builders based in Solihull, we will talk you through your options and give you a clear, itemised quote.
Call 07393 194 336Get a free quote